When I do my calculations for clients (not rocket science just personal experience in how these sales translate) I see these improvement values in Philly Homes that sell for up to 250K look like this:
Decks- (12x12 ish) add 5,000-7,000 to the sales price if it overlooks something nice- 4,000 if is is small or overlooks something not so nice
Wrap around/full size Decks made from trex or artificial wood $10-$15,000
Remodeled Kitchen with 42" cabinets, granite, GE type appliances- $8,000-$10,000 (8,000 for not eat in)
with small cabinets builder grade and lesser finishings... deduct $5,000-$10,000
with GE Profile and better appliances and European or upgraded cabinetry $12,000-$18,000
This is not science like I mentioned but those are my findings.
Hope this helps. Would be curious to see what other say.